(1) Field of the Invention
The present invention relates to a high-frequency integrated circuit module for mounting an integrated circuit (IC) which operates with high-frequency waves in a high frequency band such as a microwave band and a milliwave band.
(2) Description of the Related Art
Because of the multifunction of an IC chip which operates in a microwave band or milliwave band, one IC chip requires three or more radio frequency (RF) signal terminals. Within an IC chip, the width of RF signal terminals is narrow and therefore isolation between the RF signal terminals is assured.
In general, the thickness of a circuit board is selected so that the width of lines in a package for mounting an IC chip becomes greater than that of terminals in the IC chip in consideration of signal line connections which are made for secondary mounting. At the same time, transmission and reflection characteristics are assured. FIG. 19 shows a plan view of a prior art high-frequency IC module.
The high-frequency IC module 100 shown in FIG. 19 includes, for example, an IC chip 100; a metal plate (metal board) 101; a first ceramic plate (ceramic board) 102a molded integrally with the metal plate 101 and constituting a feed line portion for a RF signal on one side of the metal plate 101; and a second ceramic plate 102b molded integrally with the metal plate 101 and constituting a feed line portion for RF signals on the other side of the metal plate 101.
The first ceramic plate 102a is provided with a microstrip transmission line 103, which is connected with the RF signal terminal 111 of an IC chip 110 through a bonding wire. The second ceramic plate 102b is provided with three microstrip transmission lines 104, 105, and 106, which are connected with the RF signal terminals 112, 113, and 114 of the IC chip 110 through bonding wires. Note in FIG. 19 that reference numeral 107 denotes a position at which a cap for hermetically sealing the IC chip 110 is mounted.
The above-described IC chip 110 with a plurality of RF signal terminals 112, 113, and 114 on one side has, for example, the function of selecting one system from RF signals received from a plurality of systems. Such an IC chip can be applied to a high-frequency receiving circuit which employs an adaptive array antenna.
However, if the IC chip 110 is mounted on the above-described package having a plurality of microstrip transmission lines 104, 105, and 106 on one side thereof, isolation between the RF signal terminals will be degraded compared with the characteristics of the IC chip 110, because the width of the microstrip transmission lines 104, 105, and 106 on the package side is greater than that of the RF signal terminals of the IC chip 110.
That is, coupling occurs over the length of each of the microstrip transmission lines 104, 105, and 106, and resonance occurs at a frequency resulting from the line length. Because of this, the transmission characteristics degrade sharply.
FIG. 20 shows a layout in the case where an electro-magnetic simulation of microstrip transmission lines close to each other is made. The transmission characteristics obtained by the simulation are shown in FIGS. 21A and 21B. In the simulation, a ceramic board was employed and microstrip transmission lines of 0.2 mm in thickness were assumed to be arranged at the interval of 1 mm. FIG. 21A shows a reflection characteristic in the case where a RF signal (for example, 30 GHz or greater) is input to an input port xe2x80x9c1xe2x80x9d shown in FIG. 20. FIG. 21B shows a through characteristic in the case where the RF signal is input to the input port 1.
In this case, the interval between the microstrip transmission lines is narrow and therefore coupling takes place over the length of the line. As shown at reference numerals 121 to 128 in FIGS. 21A and 21B, resonance takes place at specific frequencies resulting from line length and there is a sharp degradation of transmission characteristics (reflection and through characteristics) (i.e., isolation degradation).
On the other hand, if the interval between the microstrip lines is increased to 1.5 mm and 3.0 mm, as shown in FIGS. 22A, 22B, 23A, and 23B, resonance resulting from line length is less likely to occur and that there is no isolation degradation. Note that the transmission characteristics in the case of interval=1.5 mm are shown in FIGS. 22A and 22B. The transmission characteristics in the case of interval=3.0 mm are shown in FIGS. 23A and 23B.
Thus, it is necessary that microstrip transmission lines for secondary mounting be spaced to some degree. However, since the spaces between the RF signal terminals 112, 113, and 114 of the IC chip 110 are narrow, the line space in a portion of the IC chip 110 becomes narrow. Because of this, the case of a RF signal of about a few GHz is considered practically negligible. However, in the case of a RF signal having an extremely high frequency of 30 GHz or greater, isolation degradation at the line-space narrowed portion is not negligible.
Particularly, in the case of a high frequency of 30 GHz or greater, the wavelength becomes about a few millimeters and performance depends on the size of a component such as an IC chip and a package. Therefore, when obtaining a high gain by a high-frequency flip-chip structure, there are cases where the operation of a circuit becomes unstable by the leakage of unnecessary high-frequency components.
The present invention has been made in view of the circumstances mentioned above. Accordingly, it is the primary object of the present invention to provide a high-frequency IC module which is capable of minimizing the leakage of unnecessary high-frequency components and assuring the required isolation between a plurality of high-frequency signal terminals disposed on one side portion of an IC chip, even when mounting an IC which processes high-frequency signals in an extremely high frequency band such as a microwave band and a milliwave band.
To achieve this end and in accordance with the present invention, there is provided a high-frequency integrated circuit (IC) module comprising:
(1) a multilayer mounting board on which an IC with a plurality of high-frequency signal terminals on one side portion thereof is mounted;
(2) a plurality of IC connecting portions disposed on one surface of the multilayer mounting board on which the IC is mounted, the IC connecting portions being respectively connected with the plurality of high-frequency signal terminals of the IC;
(3) a plurality of external connection terminal portions disposed on a side portion of the other surface of the multilayer mounting board which portion corresponds to the one side portion of the IC, at wider intervals than those between the high-frequency signal terminals of the IC;
(4) a plurality of high-frequency signal lines provided within the multilayer mounting board to transmit high-frequency signals;
(5) a plurality of first through holes for respectively connecting the inner ends of the high-frequency signal lines with the IC connecting portions;
(6) a plurality of second through holes for respectively connecting the outer ends of the high-frequency signal lines with the external connection terminal portions; and
(7) a high-frequency restricting member for ground-connecting both surfaces of the multilayer mounting board and restricting propagation of high-frequency signals, provided at least between the high-frequency signal lines and along the high-frequency signal lines.
In the high-frequency IC module of the present invention constructed as described above, between a plurality of high-frequency signal terminals provided on one surface of the multilayer mounting board and a plurality of external connection terminal portions provided on the other surface of the multilayer mounting board, high-frequency signals are transmitted within the multilayer mounting board through the above-described through holes and high-frequency signal lines.
In the high-frequency IC module of the present invention, the external connection terminal portions within the multilayer mounting board are disposed at wider intervals than those between the high-frequency signal terminals of the IC. Furthermore, between the high-frequency signal lines, the above-described high-frequency restricting member is provided along the high-frequency signal lines. Therefore, the high-frequency IC module of the present invention is capable of preventing unnecessary line coupling due to the propagation of the leakage components of high-frequency signals within the multilayer mounting board and also preventing a resonance phenomenon due to the occurrence of an unnecessary propagation mode.
Therefore, even in the case where an integrated circuit has a plurality of high-frequency signal terminals (for high-frequency signals in a microwave band or milliwave band) on one side portion thereof, the required isolation between signal terminals can be easily assured.
In the high-frequency IC module of the present invention, the above-described high-frequency restricting member may comprise a plurality of third through holes for ground-connecting both surfaces of the multilayer mounting board. The third through holes are provided within the multilayer mounting board and at least between the high-frequency signal lines and along the high-frequency signal lines. In this manner, the above-described line coupling and resonance phenomenon can be relatively easily prevented by employing the existing through-hole processing technique. Therefore, the manufacturing cost can be reduced.
In the high-frequency IC module of the present invention, the above-described IC connecting portions may comprise coplanar lines, respectively. The above-described external connection terminal portions may also comprise coplanar lines, respectively. In this case, the signal-line exposed portion can be minimized at both surfaces of the multilayer mounting board. Therefore, when the IC is molded with predetermined resins, the influence of resins on signal lines can be minimized and isolation degradation can be minimized.
Further in accordance with the present invention, there is provided a high-frequency integrated circuit (IC) module comprising:
(1) a primary multilayer mounting board on which an IC with a plurality of high-frequency signal terminals on one side portion thereof is mounted;
(2) a plurality of IC connecting portions disposed on one surface of the primary multilayer mounting board on which the IC is mounted, the IC connecting portions being respectively connected with the plurality of high-frequency signal terminals of the IC;
(3) a plurality of external connection terminal portions disposed on a side portion of the other surface of the primary multilayer mounting board which potion corresponds to the one side portion of the IC, at wider intervals than those between the high-frequency signal terminals of the IC;
(4) a plurality of high-frequency signal lines provided on the other surface of the primary multilayer mounting board and respectively connected at their outer ends with the external connection terminal portions;
(5) a plurality of first through holes for respectively connecting the inner ends of the high-frequency signal lines with the IC connecting portions;
(6) a secondary multilayer mounting board connected with the other surface of the primary multilayer mounting board through bumps; and
(7) a high-frequency restricting member, for ground-connecting positions between the high-frequency signal lines with the one surface of the primary multilayer mounting board and restricting propagation of high-frequency signals, provided at least along the high-frequency signal lines.
In the high-frequency IC module of the present invention constructed as described above, between a plurality of high-frequency signal terminals provided on one surface of the multilayer mounting board and a plurality of external connection terminal portions provided on the other surface of the multilayer mounting board, high-frequency signals are transmitted at the other surface of the multilayer mounting board through the above-described through holes and high-frequency signal lines.
In the high-frequency IC module of the present invention, the high-frequency signal lines are connected to the external connection terminal portions disposed at wider intervals than those of the high-frequency signal lines. The high-frequency restricting member, for ground-connecting positions between the high-frequency signal lines with the one surface of the primary multilayer mounting board and restricting propagation of high-frequency signals, is provided at least along the high-frequency signal lines. Furthermore, the high-frequency signal lines can be positioned within a closed space by a connection with a secondary multilayer mounting board. Therefore, compared with the case where high-frequency signal lines are provided within a primary multilayer mounting board, the above-described line coupling and resonance phenomenon can be prevented with a simpler structure.
Even in the case where high-frequency signal lines are provided on the bottom surface of the multilayer mounting board, the high-frequency signal lines can be positioned within a closed space by a connection with a secondary multilayer mounting board. Therefore, compared with the case where high-frequency signal lines are provided within a primary multilayer mounting board, the above-described line coupling and resonance phenomenon can be prevented with a simpler structure.
In the case where high-frequency signal lines are provided on the bottom surface of the multilayer mounting board, the outer ends of the high-frequency signal lines are formed as the external connection terminals, respectively. Therefore, compared with the case where the high-frequency signal lines are formed separately from the external connection terminals, signal transmission reliability can be enhanced and the number of manufacturing steps and the manufacturing cost can be reduced.